engine surging but no CEL

[s'ko]

ok here's one 4 the engine gurus

this is on the hi comp ej25 motor

i am driving 2 work on stop & go traffic

with the car in neutral engine starts idling @ 1200-1500 rpm.

if i blip the throttle then it will rise & stay up there.

i drove into the parking garage & it started 2 keep rising.

 

i pulled the battery wires and left it so that the ECU will reset

any thoughts?

[Suzam]

My first thought is a coolant temp sensor going bad. They aren't expensive and relatively easy to replace. I had on on a MY95 that did have similar symptoms. Never threw a CEL and once changed the idle went back to acting normal. You should do a search because I think there is a post showing the location of the sensor.

 

BTW- please keep us posted when you do track down and fix the problem so anyone else that has the same issue will know what to try.

[s'ko]

pulled out me OBD2 reader and it is showing p1507. Idle Control.

 

Searched and found a boat load of info on the error, having to do with either the neutral switch and some other issues.

 

I had a prior problem with the main engine harness plugs being wet and contaminated when I installed the engine. I have the battery pulled and the plugs unplugged. I am trying to track down a can of compressed air used for keyboard cleaning to see if I can't get it blown dry.

 

Will update when I have more news.

[Log1call]

First thing I'd do was check the throttle cable isn't sticking or that there is something jamming the pedal, anything like that.

 

Then I'd check all the small vacumm hoses on the motor.

 

That trouble code just means that the idle speed control valve couldn't keep the revs within the desired range. That code will set if the motor is idling to high or to low for whatever reason.

 

Since it came on suddenly, I'd doubt it's the valve. They usually just get dirty and cause a slightly erratic idle, not a real radical problem.

 

Edit:

Don't go condemming the throttle position sensor, temperature sensor or the neutral switch, they all have trouble codes of their own.

Edited September 16, 2009 by Log1call

[s'ko]

im a moron.

 

on the initial drive that prompted the original post, the throttle cable

worked it self loose.

when i pull the battery & looked in the engine bay, i tightened the cable so that the throttle was slightly open

when the car started again, the ECU was trying to make sense of what was going on with the throttle.

It kept trying to lower the idle & that's what caused P2507 to Show